B B Rasmussen1, R R Wolfe, E Volpi. 1. University of Southern California, Department of Kinesiology, University Park Campus, 3560 Watt Way, PED 107, Los Angeles, CA 90089-0652, USA. blakeras@usc.edu
Abstract
BACKGROUND:Muscle protein synthesis is stimulated in the elderly when amino acid availability is increased. OBJECTIVE: To determine which mode of delivery of amino acids (intravenous vs. oral ingestion) is more effective in stimulating the rate of muscle protein synthesis in elderly subjects. DESIGN:Fourteen elderly subjects were assigned to one of two groups. Following insertion of femoral arterial and venous catheters, subjects were infused with a primed, continuous infusion of L-[ring-2H5] phenylalanine. Blood samples and muscle biopsies were obtained to measure muscle protein fractional synthesis rate (FSR) with the precursor-product model, phenylalanine kinetics across the leg with the three-pool model, and whole body phenylalanine kinetics. Protein metabolism parameters were measured in the basal period, and during the administration of oral amino acids (n=8) or a similar amount of intravenous amino acids (n=6). RESULTS:Enteral and parenteral amino acid administration increased amino acid arterial concentrations and delivery to the leg to a similar extent in both groups. Muscle protein synthesis as measured by both FSR, and the three-pool model, increased during amino acid administration (P < 0.05 vs. basal) in both groups with no differences between groups. Whole body proteolysis did not change with the oral amino acids whereas it increased slightly during parenteral amino acid administration. CONCLUSIONS: Increased amino acid availability stimulates the rate of muscle protein synthesis independent of the route of administration (enteral vs. parenteral).
RCT Entities:
BACKGROUND: Muscle protein synthesis is stimulated in the elderly when amino acid availability is increased. OBJECTIVE: To determine which mode of delivery of amino acids (intravenous vs. oral ingestion) is more effective in stimulating the rate of muscle protein synthesis in elderly subjects. DESIGN: Fourteen elderly subjects were assigned to one of two groups. Following insertion of femoral arterial and venous catheters, subjects were infused with a primed, continuous infusion of L-[ring-2H5] phenylalanine. Blood samples and muscle biopsies were obtained to measure muscle protein fractional synthesis rate (FSR) with the precursor-product model, phenylalanine kinetics across the leg with the three-pool model, and whole body phenylalanine kinetics. Protein metabolism parameters were measured in the basal period, and during the administration of oral amino acids (n=8) or a similar amount of intravenous amino acids (n=6). RESULTS: Enteral and parenteral amino acid administration increased amino acid arterial concentrations and delivery to the leg to a similar extent in both groups. Muscle protein synthesis as measured by both FSR, and the three-pool model, increased during amino acid administration (P < 0.05 vs. basal) in both groups with no differences between groups. Whole body proteolysis did not change with the oral amino acids whereas it increased slightly during parenteral amino acid administration. CONCLUSIONS: Increased amino acid availability stimulates the rate of muscle protein synthesis independent of the route of administration (enteral vs. parenteral).
Authors: M A Fiatarone; E F O'Neill; N D Ryan; K M Clements; G R Solares; M E Nelson; S B Roberts; J J Kehayias; L A Lipsitz; W J Evans Journal: N Engl J Med Date: 1994-06-23 Impact factor: 91.245
Authors: Chad M Kerksick; Colin D Wilborn; Michael D Roberts; Abbie Smith-Ryan; Susan M Kleiner; Ralf Jäger; Rick Collins; Mathew Cooke; Jaci N Davis; Elfego Galvan; Mike Greenwood; Lonnie M Lowery; Robert Wildman; Jose Antonio; Richard B Kreider Journal: J Int Soc Sports Nutr Date: 2018-08-01 Impact factor: 5.150